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Lookup NU author(s): Professor Nicholas JakubovicsORCiD
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Interactions involving genetically distinct bacteria, for example between oral streptococci and actinomyces, are central to dental plaque development. A DNA microarray identified Streptococcus gordonii genes regulated in response to coaggregation with Actinomyces naeslundii. Expression of 23 genes changed >3-fold in coaggregates, including nine genes involved in arginine biosynthesis and transport. The capacity of S. gordonii to synthesize arginine was assessed using a chemically defined growth medium. In monoculture, streptococcal arginine biosynthesis was inefficient and streptococci could not grow aerobically in low arginine. In dual-species cultures containing coaggregates, however, S. gordonii grew to high cell density in low arginine. Equivalent co-cultures without coaggregates showed no growth until coaggregation was evident (9 h). An argH mutant was unable to grow in low arginine with or without A. naeslundii, indicating that arginine biosynthesis was essential for coaggregation-induced streptococcal growth. Using quantitative RT-PCR, expression of argC, argG and pyrAb was strongly (10- to 100-fold) up-regulated in S. gordonii monocultures after 3 h growth when exogenous arginine was depleted. Co-cultures without induced coaggregation showed similar regulation. However, within 1 h after coaggregation with A. naeslundii, expression of argC, argG and pyrAb in S. gordonii was partially up-regulated although arginine was plentiful, and mRNA levels did not increase further when arginine was diminished. Thus, A. naeslundii stabilizes S. gordonii expression of arginine biosynthesis genes in coaggregates but not co-cultures and enables aerobic growth when exogenous arginine is limited.
Author(s): Jakubovics NS, Gill SR, Iobst SE, Vickerman MM, Kolenbrander PE
Publication type: Article
Publication status: Published
Journal: Journal of Bacteriology
ISSN (print): 0021-9193
ISSN (electronic): 1098-5530
Publisher: American Society for Microbiology
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